An actuation apparatus and methods of operation thereof

ABSTRACT

A rotary electromagnetic actuator includes a biasing assembly for applying a torque to its rotor. Such an actuator may be used to operate a poppet valve of an internal combustion engine. The biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of potential energy in its second configuration than in its first configuration. The apparatus includes a latching mechanism for selectively latching the biasing assembly in its second configuration.

FIELD OF THE INVENTION

The present invention relates to an actuation apparatus including an electromagnetic actuator. The actuator has a rotor which is rotatable relative to a stator and the actuator includes a biasing assembly for applying a torque to the rotor. Such an actuation apparatus may be used to operate a poppet valve of an internal combustion engine for example.

BACKGROUND TO THE INVENTION

WO 2004/097184 describes a rotary electromagnetic actuator which may be used to open and close a valve of an internal combustion engine. In one example, a resilient cantilevered spring arm is in contact with the outer circumference of an eccentric surface which rotates with the rotor. The arm is deformed over part of the rotation of the rotor and thereby stores potential energy which is subsequently used to accelerate the rotor through a subsequent part of its rotation.

SUMMARY OF THE INVENTION

The present invention provides an actuation apparatus having an electromagnetic actuator comprising:

-   -   a stator;     -   a rotor which is rotatable relative to the stator over a range         of rotation of the rotor; and     -   a biasing assembly for applying a torque to the rotor over at         least part of the range of rotation of the rotor,     -   wherein the biasing assembly is moveable between a first         configuration and a second configuration, wherein the biasing         assembly stores a higher amount of potential energy in its         second configuration than in its first configuration, and     -   the apparatus includes:     -   a latching mechanism for selectively latching the biasing         assembly in its second configuration.

Under some operating conditions, it may be desirable for the biasing assembly to store potential energy and then release this energy back to the rotor during the same cycle of operation of the rotor (via exertion of a decelerating torque and then an accelerating torque on the rotor). If the rotor is operated so as to oscillate back and forth over a range of rotation, then a cycle of operation can be considered to consist of one oscillation, that is, rotation in one direction (over part of a full rotation) and then rotation back in the opposite direction to reach its original orientation. Alternatively, if the rotor is operated to rotate through a complete revolution, then a cycle of operation can be considered to be a full rotation of the rotor.

Under other operating conditions, it may be preferable to prevent the biasing assembly from applying a torque to the rotor.

According to the invention, the biasing assembly is selectively latched in its second configuration, in which potential energy is stored in the biasing assembly. In this way, the biasing assembly can be held in its “charged” configuration so that the stored energy is available for release back to the rotor when required. This avoids the need to wait for the biasing assembly to be recharged with potential energy after a period during which the operation of the biasing assembly to store and release energy has been suspended.

The apparatus may include a controller which is operable to control the latching mechanism to latch the biasing assembly in its second configuration during an oscillation of the rotor and to release the biasing assembly from its second configuration after the oscillation.

In addition, or alternatively, a or the controller may be operable to control the latching mechanism to latch the biasing assembly in its second configuration during a full rotation of the rotor and to release the biasing assembly from its second configuration after the full rotation.

Thus, energy stored in the biasing assembly during a first cycle of oscillation or rotation of the rotor may be released during the next cycle, or during a subsequent cycle following one or more intervening cycles during which the energy is stored in the biasing assembly. In this way, energy may be stored in the biasing assembly ready for release as and when required, without needing to wait for the rotor to rotate through part of its rotation during which energy is loaded into the biasing assembly.

In its first configuration, the biasing assembly may store no, or substantially no, potential energy.

When the biasing assembly moves from its second configuration to the first configuration, potential energy stored by the biasing assembly is transferred to the rotor via the application of a torque to the rotor by the biasing assembly.

The biasing assembly may be implemented mechanically, hydraulically or pneumatically, for example. Preferably, the biasing assembly is a mechanical assembly and comprises a resilient mechanical component. This component may serve to store potential energy as strain energy and to generate a biasing force which is exerted on the rotor by the biasing assembly.

It would be appreciated that the resilient mechanical component of the biasing assembly may take various forms, such as a spring or a block of resilient material.

In preferred examples, the rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the potential energy stored by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface. More particularly, the magnitude of the potential energy stored by the biasing assembly when in its second configuration may be dependent on the magnitude of the displacement of the cam follower by the cam surface from its position when the biasing assembly is in its first configuration.

The latching mechanism may include a latch member which is moveable between a first position in which it retains the biasing assembly in its second configuration and a second position where it does not impede movement of the biasing assembly between its first and second configurations.

The latching mechanism may be arranged to selectively apply a resilient biasing force to the latch member which urges the latch member towards its first position.

Thus, if the latch member is not able to move immediately towards and into its first position, the resilient biasing force acts to move the latch member towards and into that position as and when the latch member is subsequently able to do so.

The latch member may interact with the cam follower of the biasing assembly such that it restricts movement of the cam follower when the latch member is in its first position. In this way, the cam follower of the biasing assembly may be latched by the latching mechanism so as to hold the biasing assembly in the configuration in which mechanical potential energy is stored by the assembly.

In a preferred configuration, the cam follower is mounted for rotation about a pivot, the cam follower includes a profiled portion which extends radially relative to the pivot, and when the latch member is in its first position, it prevents rotation of the profiled portion around the pivot in at least one direction.

A further electromagnetic actuator may be provided in combination with the actuation apparatus, wherein the latch member is moveable between a first position in which is retains the biasing assemblies of both actuators in their second configurations and a second position where it does not impede movement of the biasing assemblies between their first and second configurations.

Accordingly, a single latch member may be used to latch the biasing assemblies of two actuators simultaneously if both actuators are performing the same operations. In such configuration, the biasing assembly of each actuator may include a cam follower, with the cam followers mounted for rotation about a common pivot. Each cam follower may include a profiled portion which extends radially relative to the pivot, and when the latch member is in its first position, it prevents rotation of each profiled portion around the pivot in at least one direction.

The present invention also provides an internal combustion engine including at least one cylinder having at least one valve and an actuation apparatus as described herein, with its actuator arranged to actuate the at least one valve. In this implementation, the biasing assembly may be employed to store and release energy to the rotor of the actuator within one valve cycle of opening and closing, or store energy during one valve cycle and then retain this energy until release thereof is required during a subsequent valve cycle.

The present invention further provides a method of operating an electromagnetic actuator comprising:

-   -   a stator;     -   a rotor which is rotatable relative to the stator over a range         of rotation of the rotor; and     -   a biasing assembly for applying a torque to the rotor over at         least part of the range of rotation of the rotor,     -   wherein the biasing assembly is moveable between a first         configuration and a second configuration, wherein the biasing         assembly stores a higher amount of mechanical potential energy         in its second configuration than in its first configuration,     -   the method comprising the step of selectively latching the         biasing assembly in its second configuration.

The biasing assembly may be latched in its second configuration during an oscillation of the rotor and then held in that configuration until it is released from that configuration by the latching assembly in a subsequent oscillation.

Similarly, the biasing assembly may be latched in its second configuration during a full rotation of the rotor and then held in that configuration until it is released from that configuration by the latching assembly in a subsequent full rotation.

For example, when the actuator is arranged to actuator valve of a cylinder in an internal combustion engine, the biasing assembly may be latched in its second configuration during a first cycle of opening and closing of the valve, and released from its second configuration during a second, subsequent cycle of opening and closing of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example with reference to the accompanying schematic drawings, wherein:

FIG. 1 is a perspective front view of a pair of rotary electromagnetic actuators; and

FIGS. 2 to 4 are front views of parts of a pair of actuators including a common latching mechanism according to an embodiment of the invention in successive stages of operation.

DETAILED DESCRIPTION OF THE DRAWINGS

In order to provide additional context for the features shown in FIGS. 2 to 4, an example of a rotary electromagnetic actuator to which the invention may be applied is shown in FIG. 1.

The actuator 2 of FIG. 1 includes a rotor 4 which is rotatably mounted in a stator 6. In the configuration shown, the stator 6 is shared with a second actuator 8. The stator includes eight coils 10 which are evenly circumferentially spaced around the rotor, with respect to the rotational axis 12 of the rotor. In operation of the actuator, a magnetically generated torque is exerted on the rotor by selectively energising the stator windings. The rotor of actuator 8 is omitted for clarity in the drawings.

A cam surface 14 is formed on the rotor. A cam follower in the form of an arm 16 is in engagement with the cam surface. The cam follower includes a roller 18 which bears against the cam surface 14. The other end of the arm is rotatably mounted on a shaft 20. Shaft 20 is supported by a bearing housing for the rotor 4. This bearing housing is omitted for clarity in FIG. 1. The exposed part of the shaft 20 is a press fit into a bore in the bearing housing.

The cam follower arm 16 is urged into engagement with the cam surface 14 by a biasing assembly 30. This assembly includes a leaf spring 32. The leaf spring is pivotably mounted on the stator 6 at a first end 34. A second, opposite end 36 of the leaf spring bears against the cam follower arm 16, urging it downwardly, towards the cam surface 14. The leaf spring, cam follower and cam surface are arranged such that the biasing assembly can exert a force on the rotor which acts to one side of the rotor axis 12, rather than towards it, so that it generates a torque around this axis.

Preferred cam surface configurations are disclosed in a co-pending UK patent application filed by the present applicants. The biasing assembly shown in FIG. 1 includes a constraining member in the form of a locking cylinder 40. This aspect is also the subject of a co-pending UK patent application filed by the present applicants.

FIGS. 2 to 4 show end views of parts of a pair of electromagnetic actuators with a common latching mechanism according to an embodiment of the invention. Other features of the actuators are omitted for clarity in the drawings.

Although the drawings depict an implementation in which a common latching mechanism interacts with two actuators, it will be appreciated that, in other examples, it may be preferable for a dedicated latching mechanism to be provided in association with each actuator of a system, so that each actuator can be latched independently of the others.

Nevertheless, in some applications, a pair of adjacent actuators may require their biasing assemblies to be latched in a disengaged orientation at the same times. In those circumstances, the use of a common latching mechanism may be beneficial relative to the use of two independent mechanisms in terms of reduced weight and cost, and simpler control. For example, the use of a common latching mechanism may be appropriate when the pair of actuators is employed to operate a pair of inlet valves, or a pair of exhaust valves, of a cylinder of an internal combustion engine.

The same reference numerals have been used in FIGS. 2 to 4 as in FIG. 1 to identify the same or corresponding features of the configuration shown in FIGS. 2 to 4.

In the configuration shown in FIGS. 2 to 4, two cam follower arms 16 are pivotably mounted on a common shaft 20. The distal end of each cam follower arm is engaged in FIGS. 2 and 3 with a respective cam surface 14 of an associated rotor 4.

In FIGS. 2 and 3, a latch member or pin 50 of a latching member is located in a position spaced from the cam follower arms 16.

The cam follower arms 16 differ from the arm shown in FIG. 1 in that they also include profiled portions or lugs 52 and 54. Lug 52 is an integral part of the cam follower arm on the right hand side of FIG. 2, whilst lug 54 is an integral part of the cam follower arm on the left of FIG. 2. Each lug extends or projects from the associated cam follower arm in a radially outward direction relative to shaft 20.

Each of the cam follower arms 16 is biased in a direction which urges the respective roller 18 into engagement with the corresponding cam surface 14. This biasing force is provided by a respective biasing assembly (not shown) which engages with a projection 56, 58 formed on each cam follower arm.

With the latch member 50 in its disengaged position as shown in FIGS. 2 and 3, it can be seen that the cam follower arms are able to pivot around the shaft as the radius of the cam surface 14 increases and decreases. In the configuration of FIG. 3, the cam follower arms are upwardly pivoted as the rollers 18 are in engagement with raised portions 60 and 62 of the cam surfaces 14. As a result, the portions of the respective biasing assemblies which are in engagement with projections 56 and 58 are displaced. This results in storage of mechanical potential energy in a resilient component of each biasing assembly. This may be in the form of a resilient mechanical component, such as leaf spring 30 shown in FIG. 1.

A latching mechanism including latch member 50 is operable to drop or push the latch member in a direction towards shaft 20. This moves the member from the location shown in FIG. 3 in which it is spaced from the cam follower arms, to the position shown in FIG. 4, in which it is located between the lugs 52 and 54. When the latch member is in the position shown in FIG. 4, it blocks the cam follower arms from rotation towards the respective rotors 4 under the influence of the respective biasing assemblies. In this position, the latch member latches each biasing assembly in a configuration in which it stores mechanical potential energy. Therefore, as shown in FIG. 4, when projections 60 and 62 subsequently rotate away from rollers 18, the rollers are prevented from following the decrease in the radius of the cam surfaces 14.

As can be seen in FIG. 4, each lug is located on the opposite side of the latch member to the respective cam follower arm. Therefore each biasing assembly acts to urge the lugs towards each other and so the latch member is pinched between the two lugs and blocks both of them from further rotation.

The latching mechanism may be employed to retain the cam follower arms in the raised positions shown in FIG. 4 when one or more cycles of operation of the rotors 4 are required to take place without deployment of the torque and energy recycling afforded by the respective biasing assemblies. As and when the respective actuators subsequently need to carry out a cycle in which it is desired to transfer the energy stored in the respective biasing assemblies to the rotors, the latching mechanism retracts the latch member 50 from the engaged position shown in FIG. 4 to the disengaged position shown in FIGS. 2 and 3.

The latch mechanism may include a bidirectional actuator for moving the latch member 50 from one position to the other. The actuator may be an electromagnetic actuator such as a solenoid, for example, or alternatively it may be in the form of a pneumatic or hydraulic actuator.

The latching mechanism may be configured such that it is operable to resiliently urge the latch member 50 towards its engaged position. Accordingly, if the latch member is not initially able to move into its engaged position because either or both lugs 52 and 54 are positioned as shown in FIG. 2, then the latching mechanism acts to urge the pin against the upper surfaces of the lugs so that it moves into its engaged position as and when the lugs move apart and energy is stored in the biasing assemblies.

The latching mechanism may be controlled so as to only move from its engaged to its disengaged position when rollers 18 are close to or engaged with respective raised portions 60 and 62 of the cam surface. This ensures that the energy stored in the biasing assemblies is transferred to the respective rotors. 

1. An actuation apparatus having an electromagnetic actuator comprising: a stator; a rotor which is rotatable relative to the stator over a range of rotation of the rotor; and a biasing assembly for applying a torque to the rotor over at least part of the range of rotation of the rotor, wherein the biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of potential energy in its second configuration than in its first configuration, and the apparatus includes: a latching mechanism for selectively latching the biasing assembly in its second configuration.
 2. The apparatus of claim 1, wherein the apparatus includes a controller which is operable to control the latching mechanism to latch the biasing assembly in its second configuration during an oscillation of the rotor and to release the biasing assembly from its second configuration after the oscillation.
 3. The apparatus of claim 1, wherein the apparatus includes a controller which is operable to control the latching mechanism to latch the biasing assembly in its second configuration during a full rotation of the rotor and to release the biasing assembly from its second configuration after the full rotation.
 4. The apparatus of claim 1, wherein the biasing assembly comprises a resilient mechanical component.
 5. The apparatus of claim 1, wherein the rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the potential energy stored by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface.
 6. The apparatus of claim 1, wherein the latching mechanism includes a latch member which is moveable between a first position in which the latch member retains the biasing assembly in its second configuration and a second position where the latch member does not impede movement of the biasing assembly between its first and second configurations.
 7. The apparatus of claim 6, wherein the latching mechanism is arranged to selectively apply a resilient biasing force to the latch member which urges the latch member towards its first position.
 8. The apparatus of claim 6, wherein the rotor defines a cam surface and the biasing assembly includes a cam follower in engagement with the cam surface, and the magnitude of the potential energy stored by the biasing assembly is dependent on the magnitude of the displacement of the cam follower by the cam surface, wherein the latch member restricts movement of the cam follower when the latch member is in its first position.
 9. The apparatus of claim 8, wherein the cam follower is mounted for rotation about a pivot, the cam follower includes a profiled portion which extends radially outwardly away from the pivot, and when the latch member is in its first position, it engages with the profiled portion and prevents rotation of the profiled portion around the pivot in at least one direction.
 10. A combination of the apparatus of claim 6 and a further electromagnetic actuator, wherein the latch member is moveable between a first position in which the latch member retains the biasing assemblies of both actuators in their second configurations and a second position where the latch member does not impede movement of the biasing assemblies between their first and second configurations.
 11. The combination of claim 10, wherein the biasing assembly of each actuator includes a cam follower, and the cam followers are mounted for rotation about a common pivot.
 12. The combination of claim 11, wherein each cam follower includes a profiled portion which extends radially outwardly away from the pivot, and when the latch member is in its first position, it engages with each profiled portion and prevents rotation of each profiled portion around the pivot in at least one direction.
 13. An internal combustion engine including at least one cylinder having at least one valve and the actuation apparatus of claim 1, wherein the actuator is arranged to actuate the at least one valve.
 14. An internal combustion engine including at least one cylinder having at least two valves and the combination of claim 10, with each of the actuators arranged to actuate a respective valve.
 15. A method of operating an electromagnetic actuator comprising: a stator; a rotor which is rotatable relative to the stator over a range of rotation of the rotor; and a biasing assembly for applying a torque to the rotor over at least part of the range of rotation of the rotor, wherein the biasing assembly is moveable between a first configuration and a second configuration, wherein the biasing assembly stores a higher amount of mechanical potential energy in its second configuration than in its first configuration, the method comprising the step of selectively latching the biasing assembly in its second configuration.
 16. The method of claim 15, wherein the biasing assembly is latched in its second configuration during an oscillation of the rotor and the method comprises a further step of releasing the biasing assembly from its second configuration after the oscillation.
 17. The method of claim 15, wherein the biasing assembly is latched in its second configuration during a full rotation of the rotor and the method comprises a further step of releasing the biasing assembly from its second configuration after the full rotation.
 18. The method of claim 15, wherein the actuator is arranged to actuate a valve of a cylinder in an internal combustion engine.
 19. The method of claim 18, wherein the biasing assembly is latched in its second configuration during a first cycle of opening and closing of the valve, and released from its second configuration during a second, subsequent cycle of opening and closing of the valve. 